1. Field of the Invention
The primary application of this interlock system is to interlock two or more shafts on film editing tables. It is now possible to interlock drive motors of these tables at very high expense and using very complex and more costly electronics. With the present invention, the system can be greatly simplified and can be produced far less expensively while improving precision. The system derives information from editing Table I and feeds the information to Table 2. As the picture and sound from Table 1 move, Table 2 will follow. This aids in synchronizing several picture and sound tracks.
Another film application is to lock together film reproducers so that a final mix can be performed. Sound tracks which have been recorded on sprocketed magnetic film are edited and aligned with the film. These tracks must be played back in interlock or synchronism to mix the film. The audio from the sound tracks are fed into an audio mixer and the film is then viewed. This enables the mixer to adjust audio levels so that they match with the picture. An example would be having a door close. If it were out of synchronism, or too loud or too soft, it would be very obvious to the audience. Since many elements are used in making a film, each element must be worked with separately. Thus, the music, sound effect, dialogue, and narration are derived from separate tracks and are synchronously mixed. To maintain synchronism, interlocked motors are used to drive the film.
Other applications include machine tools that are computer controlled. This interlock system can follow signal pulse lines very accurately with very little overshoot. Similar applications exist in robotics where several motors must be controlled with a simple interlock system. Mechanical arms to lift and maneuver heavy objects with precise accuracy and aircraft servos where lightweight accurate stable servos are needed are other exemplary applications.
In each of these applications the interlock package forming the present invention is used to lock together two or more servo systems. The unit takes information from the line or remote encoder which is representative of the speed of rotation of the remote or master shaft and compares it to the local encoder output which is representative of the speed of rotation of the local or slave shaft, to derive a control error signal. When the difference is zero, the two shafts are, of course, in synchronism thus giving an accurate interlock between the systems. In practice, however, imperfection of components, and drift with time requires means for achieving greater precision than heretofore possible.
It is an object of the present invention to provide such a system having such means for affording greater precision of synchronous shaft control at reduced cost.